Yes, these are the old slavic ruins of VranĂk. To be honest, I don´t think we will see them in the game. I think the western riverside of sazava will not be a part of the playable area. A river is a perfect natural border for a game, and to be honest, this old and difficult to mention slavic ruins and the little village of VranĂk are not so important to be a part of the game.
The old map was 9km², the new one is around 16km² and added the upper right quarter of the map with Uzice and the surrounding landscape. If the western riverside was part of the originally game concenpt, than a new 16km² landscape is not possible with only adding the upper right quarter of the map, so the other riverside was not planned to be a playable area at the beginning. Maybe now it is, but I doubt it, I think we will not to able to cross Sazava river, and so on we will not to be able to visit the this old slavic ruins. Nevertheless, the ruins are there.
But there are also some slavic ruins in Ledecko too, we may will see in the game as we still can see them today. But it is possible that this ruins are newly excavated and were forgotten during the late mediaeval times.
On the other hand, It could be possible that the western sazava riverside is now a part of the newly 16km² map. The sneaky wriggle weasel knows much, but he don´t know about this.